Molding conduits



July 7, 15925.

J. F. MURRAY HOLDING CONDUITS Filed Sept. 9, 1924 Patented'July 7, 1925.

UNITED STATES I l JOHN r. MURRAY, or

i HOLDING 1,544,855 PATENT OFFICE.

BROOKLYN, NEW YORK.

CONDUITs.

Application filed September 9, 1924. Serial No. 736,691.

which'the following is a specification.

In an application of Thomas E. Murray, No. 670,423, there is deseribeda method of moldingconduits by thel use of an elastic l and highly resilient tubular core of suffu .'sure of plastic-material and of such a coml cient strength to support the external .presposition that when pulled endwise it will contract transversely so as to break its ad- 'hesion tothe surrounding material and permit its removal. Such a core, for long conduits, is generally made of high grade rubber composition. One difficulty with cores of this sortwhere they are of sub. stantial length is Ythat they do not naturally lieflat and straight, probably owing to internal strains set up in the process ofl manufacture. In fact, such tubing will not naturally. assume or retain any predetermined line. I propose, therefore, to provide means for holding such cores in the desired line during the casting operation. The inven# tion is of particular utility in building concrete 'floors and the like with conduits therein for electric wires because in such structures the conduits, and consequently c the cores, are of comparatively small diameter and great flexibility, and also because it is important to keep theconduit along a determine/d line.- The accompanyingv drawings illustrate embodiments of the invention. Fig. 1 is a plan and Figs. 2, 3 and 4 are transverse sections illustrating an -intermediate stage inthe process. Fig. 5 is a plansimilar to'Fig. 1, illustrating a different application of the invention.

In'building the floor of a house a bottom layer, 1 of concrete, is cast on a formor center to a desired level at which the conduit is to be located. The flexible core 2 is laid on this lower body of concrete. Supse that .the conduit is to comprise a central strai ht portion connected by curves at the en s to outlet boxes 3. The core is laid approximately on the desired line and is then adjusted accurately and held in position. The holder is a rigid device emform o fa'n inverted trough which ma be o f metal' or wood or other material ullicientlyrigid to resist the tendency of the core -to get out of line. The holder. extends down over the upper part ofthe core, but v leavesthe lower part exposed at the 'sides so that -the next layer of concrete 5 may be cast so as to embrace thesides of the core to a suflicient height to hold it in line. After this has been done the holder is lifted out of place and the concrete filled up to the desired level and topped olf with a iinishing coat 6.

/The holder may be of various shapes in cross-section. Fig. 3 shows it as an inverted trough 4 with vertical flanges 7 extending downward along the side edges. Fig. 4 shows the holder in the form of a channel with a web 8A resting on the curve and s1de flanges 9 extending down alongside of the same.

Fig.v 5 illustrates the application of a holding d evice 4 similar in cross-section to .that of Flg. 2 but extending longitudinally 1n a curved line. It will often be suilicient to hold the core on the curves and to leave 1t free between the curves and under such tension as to hold it approximately straight wlthout special holding devices embracin Or, we may have straight holding dev1ces like 4: for the straight portions and curved devices like 4. forthe'curved portions so as to provide external control continuously throughout the length of the core. The holding devices may conveniently be made of ordinary commercial steel shapes.

' That in Fig. 2" is a-commercial angle iron,

for example. The shapes in Figs. 3 and -l may be rolled or may be easily bent up from sheet metal. All these shapes may, as above explained, be built of other materials than metal, They must be heavy enough to hold the core in line.

Although I have described with great particularity and detail certain embodiments in my invention, yet it is not to be understood therefrom that the invention is restricted to the particular embodiments disclosed. Various modications thereof may be made by those skilled in the art without departure from the invention as defined in the following claims:

1. The lcombination with a flexible core for molding conduits of a rigid holding means adapted to extend along the core and to embrace it so as to hold it in line'.

lll

` terial to be cast about the lower sides of it to hold it in line when the holding device is subsequently withdrawn.

3. The combination with a -iiexible core for molding conduits of a trough-shaped holding device adapted, in inverted position, to cover the core and to hold it in line.

4. The combination with a flexible core for molding conduits of a holding device of substantially rigid material curved longitudinally and adapted to engage and hold such flexible core 1n a corresponding curve. 5. The method of molding conduits which consists in casting a layer of plastic material, laying thereon a iiexible core, holding said core in line while leaving the lower part thereof accessible for casting plastic material about the lower part of the core to hold it in line, and finally withdrawing 'the first holding means and completing the casting' of the plastic material about the core.

In witness whereof, I have hereunto signed my name. v u

JOHN F. MURRAY. 

